MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY ili 
4. The genera here proposed would, under all circumstances, be treated at least as 
subgenera under Potentilla, just as some of them were treated by Torrey and Gray in 
their Flora. If they can be characterized and distinguished from each other as sub- 
genera, there is no reason for withholding from them generic rank, and the classifica- 
tion will be much simpler. 
5. As far as our American species are concerned the genera proposed here are well 
defined and can be readily separated by their general habit as well as by their floral 
characters! They can be distinguished from the others much more readily than Jvesia 
ean from either Horkelia or Potentilla. 
Potentilla arguta and its allies differ from Potentilla proper by the nearly basal style, 
ascending and orthotropous seeds, the flat disk-like anthers, the arrangement of the 
stamens in five festoons, and in general habit. 
Potentilla tridentata differs by the lateral style, hairy achenes, ascending and amphi- 
tropous seeds, shrubby habit, and leaflets that are jointed to the rachis and at last decid- 
uous. 
Potentilla fruticosa and some Asiatic species differ by the same characters as the 
last (except the leaves), by the arrangement of the stamens in five festoons, and the 
scarious more or less sheathing stipules. 
Potentilla Anscrina, Egedii and anserinoides by the lateral style, thick corky achenes, 
ascending and amphitropous seeds, and (at least from all American Potentillae) by the 
fact that they propagate like Mragaria by true runners. 
Ivesia depauperata and I. sabulosa differ from all the other Ivesiae by their narrowly 
linear petals, the two pistils and the peculiar structure of the hypanthium, deseribed 
later. 
Tvesia santolinoides differs by its anthers, which are obeordate and open by a sub- 
terminal pore, by the Potentilla-like flowers, solitary style and the general habit and pe- 
culiar leaves. 
When comparing the original species of Horkelia and Ivesia, viz., H. Californica 
Cham. & Schlecht, and I. Gordonii (Hook.) T. & G. with each other and with a typical 
Potentilla, no one would hesitate to call them good genera. There are, however, species 
so intermediate between Ivesia and the other two genera, that the differences are 
nearly obliterated. This is especially the case with the distinctive lines between [vesia 
and Horkelia. Horkelia tridentata, H. congesta and H. Howellii have only 4-15 pistils 
and the two first only slightly dilated filaments. This is also the case with my H. ar- 
gyrocoma, Which is in all respects a good Ivesia, belonging to the same group as iE 
Three of them were recognized by Torrey and Gray as subgenera. 
